The homeodomain-containing transcription factor Chx10 is a central regulator of retinal development. Much of what we know about Chx10 function comes from studies using ocular retardation J (orJ) mice, which have a null mutation in the Chx10 gene. Work from our laboratory has contributed to an understanding of its role in retinal progenitor cell (RPC) proliferation and cell cycle progression. Additionally, our work and others reveal that Chx10 also influences the timing of neurogenesis, maintains neuroretinal identity, regulates adult retinal stem cells, and is required for bipolar cell formation. The primary goal of our work is to uncover the specific Chx10-dependent molecular mechanisms and pathways driving retinal development. One challenge in achieving this goal is that multiple alterations in RPC properties (assessed in orJ mice) overlap in time and initiate early in retinal development. Because of this, it is not known if these changes are mediated by shared mechanisms and whether Chx10 is required for regulating RPC properties at later stages of development. To resolve these issues and gain insight into molecular mechanisms of Chx10 function, we propose three aims. In Aim 1, we will perform a series of genetic experiments using a conditional allele of Chx10 and chimeric mice to determine developmental stages when Chx10 required in RPCs and to determine if RPC changes induced by Chx10 loss are due solely to cell-autonomous mechanisms. In Aims 2 and 3, we investigate two potential mechanisms of Chx10 function. Aim 2 builds on our recent study of hedgehog signaling indicating that loss of Chx10 influences the efficiency of signaling pathways important for proliferation. Using culture assays and gene expression measurements, we will investigate how Chx10 interacts with the hedgehog pathway. In Aim 3, we investigate a potential interaction between Chx10 and the homeodomain-containing transcription factor Lhx2 (an essential regulator of early eye development) using genetic approaches in mice. Our studies have the potential to provide a rich map of the complex mechanisms controlling formation of the retina and could provide insights into the refined use of stem cells for treating retinal disease. PUBLIC HEALTH RELEVANCE: Microphthalmia is a congenital anomaly in which the eye fails to grow to its normal size. Ocular malformations, which include microphthalmia are reported to be as high as 1 in 5000 births and children born with these malformations are often severely visually impaired or blind. The goals of the research proposed here are to understand the basis for these defects with the hope of one day developing a restorative treatment or cure for these devastating disabilities.